There are a number of instances where ultrasonic transducer assemblies are used for sensing positions, and in the case of vehicular use, ultrasonic transducers are used as in sonar assisted reversing systems in which ultrasonic transducers, controlled by microprocessors monitor a vehicle's path during any reversing maneuver and when it detects a presence of a moving or stationary object, computes the distance and provides a display to the driver and with also possible warning systems. In such systems, when a reverse gear is engaged, an "eye lid" cover protects the sensor from road dirt and damage flips up out of the way so as to permit ultrasonic systems to immediately go into operation.
In my above-identified application, a beam transformer is positioned in the near field of the ultrasonic transducer so as to unidirectionally expand the beam to thereby transform the narrow beam to a broad beam with the beam transformer being an effective coupling element for the emitted beam and the return echo for the sensing and ranging systems which both do not have significant alignment problems. Dirt, road grime and the like which can collect on an unprotected reflecting surface can seriously interfer with the operation thereof and water and moisture can adversely affect operation of the electrostatic transducer.
According to the present invention, the conical surface of the beam transformer is mounted on the interior of a closure member or end cap that seals the transducer and any associated mechanism from the environment during non-operating periods and which is moved by a solenoid or motor into the prescribed position via rotational (hinged) motion or linear (piston-like) or rack and pinion motion prior to operating periods. Suitable O-ring or gasket sealing elements preserve water tight integrity during non-operating periods.
In one particular system incorporating the invention, a school bus is provided with one or more transducer assemblies including an electrostatic beam generator and a beam transformer, which are translated to an operative position below the bus where, in conjunction with a microprocessor, it takes an acoustic image before the bus door is opened and, again, before resuming forward motion to detect students who may have crawled under the bus while it was stopped.
On cars, trucks and the like, the ultrasonic transducer can be used to measure distances for back-up purposes or for parking systems to detect object to the rear or front of the vehicle and provide indications of same to the driver.
Thus, an object of the invention is to provide an improved ultrasonic transducer assembly which, during non-operating periods is maintained clean and in a water tight condition so as to maintain efficient operation thereof.